Patients with a wide variety of malignant neoplasms display circulating sensitized lymphocytes which are spcific for antigens on the autochthonous tumor cells of the patients. In vitro assays of the cytotoxicity of such lymphocytes aginst autochthonous tumor cells reveal that cytotoxicity is significantly increased by prior in vitro activation of the lymphocytes by phytohemagglutinin. Preliminary results suggest that the parenteral administration of phytohemagglutinin to animals bearing tumor or to patients with disseminated cancer may similarly result in favorable in vivo tumor responses, but such tumor effects of phytohemagglutinin in vivo are limited by the absorption of phytohemagglutinin onto cells other than lymphocytes, and by the development of antibodies directed against phytohemagglutinin. This limitations have recently been overcome in our laboratory by the development of a procedure in which large numbers of lymphocytes from patients with disseminated carcinoma or sarcoma can be isslated and activated in vitro with phytohemagglutinin, and can then be re-infused into the patient without deleterious or toxic effects. In a clinical pilot study in which this immunotherapy was utilized in selected patients who had disseminated carcinoma or sarcoma with multiple distant pulmonary metastases, 3 of 5 patients displayed partial regressions in tumor size after re-infusions of small numbers of activated autochthonous lymphocytes These data have been extended in a clinical study of local immunotherapy of cutaneous metastases. It is now necessary to compare the immunotherapeutic effects of larger numbers of re-infused activated lymphocytes with sham-activated and non-activated lymphocytes, utilizing the IBM blood cell separator to collect 10 to the 11th power minus 10 to the 12th power peripheral blood lymphocytes for in vitro activation and subsequent re-infusion.